1. Field of the Invention
The present invention relates to the use of a high energy electron beam to chemically transform or destroy certain types of hazardous waste, and more particularly, to a flood beam electron gun that efficiently generates a source for the high energy electron beam.
2. Description of Related Art
Volatile organic compounds (VOCs) exist in the form of gasses that are emitted or vaporized from hazardous or toxic waste materials. Since these VOCs pose a significant health risk to individuals and to the environment, it is necessary to contain, extract and collect the hazardous materials so as to prevent spreading of the VOCs into the air and/or ground water. Once contained, the VOCs can be remediated by converting them into less hazardous materials that can be disposed of with substantially reduced risk.
One such remediation technique involves the injection of a high energy electron beam into a detoxification vessel containing the VOCs. Interaction between the electrons of the beam and the VOCs causes chemical transformation of the VOCs in three significant aspects, including: (1) direct de-chlorination resulting in inorganic chloride ions and reactive organic intermediates which are further degraded into non-reactive compounds; (2) production of organic and inorganic free radicals and ions which are reactive and whose reactions result in destruction of the target hazardous materials; and (3) formation of aqueous electrons (in the presence of water vapor) capable of reducing chemical bonds. An example of a toxic remediation device comprising an electron emitting source coupled to a detoxification vessel is disclosed in U.S. Pat. No. 5,319,211.
In order to achieve a sufficient level of remediation within the detoxification vessel, it is desirable to provide an electron beam having relatively high energy (such as 220 kilovolts or higher). Within the microwave tube art, electron guns are known to provide a high voltage, pencil-shaped electron beam. Such conventional pencil-shaped electron beams are undesirable electron sources in this application, since the highly focused beams tend to concentrate all their energy into a relatively small region of the vessel. As a result, only a portion of the electrons of the concentrated beam ultimately interacts with the VOCs, with the remainder being dissipated into the vessel walls in the form of thermal loss. In addition, the electron gun operates in a vacuum environment, and the electrons of the beam must pass through a vacuum barrier to the non-vacuum environment within the detoxification vessel. Conventional vacuum barriers do not permit electrons to transmit therethrough without significant additional energy loss to the barrier structure.
Thus, a critical need exists for a high voltage electron gun for use with a detoxification vessel for remediation of VOCs from hazardous or toxic waste. Such an electron gun should be capable of efficiently conducting a relatively broad electron beam into the vessel without undesired energy loss.